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You may get some movement in serps from this, it seems that some believe 301's are just as good as passing ranking value, but others believe you only get about 80-90% percent of the original value. Either way, it shouldn't be a huge difference. All the best.

Thank You for your advice. There is no need for change but the change is not avoidable,with new CMS we will have 22 languages + unicode characters in urls + different url structure. If I choose to keep some of the old urls (edit new ones maually so they are the same as old ones) and for the rest of the site I let the CMS create new ones, what do You think would I have a problem with Google? The url difference is what I am concerned about,do search engines follow some url logic when indexing a site? To explain it better: I have city listing url the old one that is ranking high has following url: domain.com/keyword/city-name -the new ones are having : domain.com/country/city-name/keyword If I decide to keep the old one for serbian language for example and let the CMS create new urls for other languages,would that be ok in terms of SEO?